One in Seven Americans Age 71 and Older Has Some Type of Dementia,
NIH-Funded Study Estimates

BETHESDA, Md., Oct. 30, 2007--A new analysis suggests that about
3.4 million Americans age 71 and older — one in seven people
in that age group — have dementia, and 2.4 million of them
have Alzheimer's disease (AD). The study, supported by the National
Institutes of Health (NIH), is the latest in a series of analyses
attempting to assess the prevalence of dementia and AD, the most
common form of dementia. Published online this week in
Neuroepidemiology, the study is the first to estimate rates of
dementia and AD using a nationally representative sample of older
adults across the United States.

Brenda L. Plassman, Ph.D., of Duke University Medical Center,
with Kenneth M. Langa, M.D., Ph.D., and David R. Weir, Ph.D., of
the University of Michigan, Robert B. Wallace, Ph.D., of the
University of Iowa, and others, conducted the analysis as part of
the Aging, Demographics and Memory Study (ADAMS). ADAMS is a
sub-study of the larger Health and Retirement Study (HRS), the
leading resource for data on the combined health and economic
circumstances of Americans over age 50. ADAMS and the HRS are
sponsored by the National Institute on Aging, a component of NIH,
under a cooperative agreement with the University of Michigan.

The study highlights the nationwide reach of dementia, which
affects not only those with the disease, but their families and
communities as well. "As the population ages during the next few
decades, the prevalence of Alzheimer's disease will increase
several-fold unless effective interventions are discovered and
implemented," said NIA Director Richard J. Hodes, M.D. "These data
underscore the urgency of research in this area."

The study included 856 HRS participants age 71 and older from 42
states in 2001-2003. ADAMS interviewers from Duke University
Medical School conducted at-home evaluations to gather information
about each participant's cognitive and functional status and
symptoms, neuropsychiatric symptoms, current medications, medical
history and family history of memory problems. Prior neuroimaging
and laboratory results were also obtained.

A team of clinicians reviewed the evaluation information and
made a preliminary assessment of each person's cognitive status. A
consensus panel of other medical experts then used well-accepted
diagnostic criteria to determine if the participant had normal
cognitive function, cognitive impairment without dementia, or
dementia. Such criteria further were used to discern the type of
dementia, including AD or vascular dementia, the second most common
cause of dementia in older adults.

Based on the experts' classifications, Drs. Plassman and Langa
and co-authors estimated the national prevalence and total numbers
of people age 71 and older, by age group, with any dementia and
with AD or vascular dementia in 2002. According to their
calculations, 13.9 percent of Americans age 71 and older have some
type of dementia, 9.7 percent of Americans in that age group have
AD, and 2.4 percent have vascular dementia. AD accounted for about
70 percent of all dementia cases among people 71 and older.

As in other studies, the ADAMS analysis showed that the
prevalence of dementia increases significantly with age. Five
percent of people ages 71 to 79, 24.2 percent of people 80 to 89,
and 37.4 percent of those 90 years or older were estimated to have
some type of dementia. The estimated rate of Alzheimer's also rose
greatly with older age — from 2.3 percent of people ages 71
to 79 to 18.1 percent of people 80 to 89 to 29.7 percent of those
age 90 and older. The ADAMS investigators found fewer years of
education and the presence of at least one APOE e4 allele, a
genetic risk factor for AD, to be strong predictors of AD and other
dementias.

Richard Suzman, Ph.D., director of NIA's Behavioral and Social
Research Program, which jointly directs the HRS, said the ADAMS
data will prove particularly valuable not only in assessing the
prevalence of dementia, but also its impact. "ADAMS, with its link
to the data about the health, economic, and family resources of
individuals in the study, will help us to characterize more fully
the burden of dementia on individuals, caregivers and the nation's
health care system," he says.

The ADAMS report is the latest published study to estimate the
prevalence of dementia and AD among older Americans. "These
assessments have provided a range of estimates, based on differing
methodologies and approaches," explains Dallas Anderson, Ph.D.,
program director for population studies in NIA's Dementias of Aging
Branch. For example, some studies have included lower age ranges
than ADAMS or broader characterizations of dementia, or have
sampled participants in a specific community as a base for national
extrapolations. A study reported in 1998 (Brookmeyer et al., 1998)
combined incidence data from four community-based studies,
estimating that national Alzheimer's prevalence among individuals
age 60 years or older would rise from 2.3 million in 1997 to 8.6
million in 2047. Widely cited estimates based on the prevalence of
Alzheimer's disease in a Chicago-based community (Hebert et al.,
2003), and an earlier comparable study using data from East Boston
(Evans et al., 1990) forecast the number of those age 65 or older
with AD to be 5.1 million in 2010.

Despite the varied approaches and findings, however, NIA experts
point out, the numbers of people with dementia, and Alzheimer's
specifically, will certainly increase until ways to delay the
progression or prevent the dementia are found. Advancing age is the
most common known risk factor for Alzheimer's disease.

The HRS is an ongoing national survey of 22,000 adults age 51
and older that began in 1992, providing data that helps
researchers, policy makers and others understand the life
circumstances of older adults and help address the challenges of
the nation's rapidly aging population. The ADAMS and HRS data are
made publicly available to researchers seeking to conduct studies
about the older U.S. population. For further information about the
HRS and ADAMS, visit hrsonline.isr.umich.edu or www.nia.nih.gov/ResearchInformation/HRS.htm.

To reach the investigators, contact Diane Swanbrow, Institute
for Social Research, University of Michigan, at 734-647-9069 or
swanbrow@umich.edu.

NIA leads the federal effort supporting and conducting research
on aging and the medical, social and behavioral issues of older
people, including AD and age-related cognitive change. For
information on dementia and aging, please visit NIA's Alzheimer's
Disease Education and Referral Center at www.nia.nih.gov/alzheimers,
or call 1-800-438-4380. For more general information on research
and aging, go to www.nia.nih.gov. Please visit the Web
sites to sign up for e-mail notification of new information and
publications about aging and about age-related cognitive
change.

The National Institutes of Health (NIH) — The Nation's
Medical Research Agency — includes 27 Institutes and Centers
and is a component of the U.S. Department of Health and Human
Services. It is the primary federal agency for conducting and
supporting basic, clinical and translational medical research, and
it investigates the causes, treatments, and cures for both common
and rare diseases. For more information about NIH and its programs,
visit www.nih.gov.